Enable writing to STDOUT with VBoxManage clonehd in raw format

It would be nice to be able to stream a virtual disk to STDOUT in raw format. This would be the opposite of the 'convertfromraw stdin' command.

I was unable to do this using VBoxManage 3.1.6 on a Linux host. I tried using '-' as the output filename; I tried using a named pipe with and without the --existing option. All of these attempts failed with various errors.

For example, the scenario in which I found myself looking for this functionality was where an operating system refused to install itself to anything less than a complete disk. I installed it to a virtual disk through VirtualBox and wanted to stream the first/primary partition to a partition on the physical hard drive. Something like: